P-38 as a bomber?

[tomo pauk]

An invitation for a discussion about Lockheed P-38's capabilities as a bomber (short/medium/long range), both historical and otherwise

 

[davebender]

USA had several purpose built twin engine bombers. Why would we try to jury rig a high altitude interceptor for use as a light bomber?

 

[pattle]

Some people see the P38 being used as a Mosquito type bomber, I think the answer is that if the Americans had wanted such a plane they would of manufactured one.

 

[wuzak]

The P-38 was used, at times, as a bomber.

An attack against Ploesti comes to mind.

 

[norab]

actually P-38's were used as bombers, led by "Droop Snoots"

some details here

Lockheed P-38 Droop Snoot

 

[pattle]

This drop snoot idea seems like something that would be done if there was a shortage of purpose built bombers, but only there wasn't a shortage of purpose built bombers.
I will have to read my big P38 book again.

 

[Shortround6]

P-38s were used as bombers using both the droop snoots with visual bomb sights and a version with radar in the nose.

A problem with trying to replace medium bombers with P-38s instead of using the P-38s in addition to the Medium bombers is the P-38 had a rather limited range on internal fuel for a bomber and limited under wing storage/hard points. 2 bombs (pick a size) OR two drop tanks OR 1 bomb and 1 drop tank.

 

[tomo pauk]

Thanks for the feedback.
Now about the capabilities - there was a modification that enabled the P-38 to carry 4 x 1000 lbs of bombs, plus drop tanks (those would be obviously of smaller volume, probably 2 x 75 gals, and dropped before dropping the bombs). picture, source

Pictures of USAF aircraft, including the P-38s for mission against Ploesti (300 gal DT + 1000 lbs bomb - asymmetric load with almost twice the DT fuel weight than bomb weight) from Foggia, 1500-1600 miles in both directions. And, a P-38 with 6 x 500 lbs bombs. Here, scroll a bit.

 

[Shortround6]

At the end of AHT there are some mission radius charts which we have referred to before. They give the combat radius of a late model P-38 with 410 US gallons of fuel as 250 miles with a pair of 1600lbs ( assumed, bomb load is given as 3200lbs) at an altitude of 10,000ft and an IAS of 210mph at 10,000ft. They do include the 20 minutes of combat ( 5 min at WEP and 15 min at military) but do NOT include form up time or evasive maneuvers or allowances.

Another chart gives a 200 mile radius at 25,000ft with a pair of 1000lb bombs (assumed, bomb load is given as 2000lbs.)

Please note that the US 1600AP bomb was 14in in diameter while the 1000lb SAP M59 bomb was 15in diameter and the 1000lb MK 36 GP bomb was 18.6 in in diameter. The US 500lb AN-M64 GP bomb was was 14in in diameter.

Granted nose shape, tail shape (taper) and fins all contribute to differences in drag, but a P-38 with six 500lb bombs isn't going very far or very fast.

B-25C/D Mitchell's were supposed to have a range of 1500 miles with 3000lbs of bombs.


B-25J was supposed to have a Range 1275 miles with 3200 pounds of bombs ( two 1600lb APs again?) Normal load was three 1000lb bombs.

But also note that the 1600lb AP carried less explosive than the 500lb GP bomb. The 1600lb bomb was much beloved by chart makers and spec writers but was seldom used in action as there were few targets that required it.

B-26s were a bit shorter ranged than the B-25s but still around 1100 miles with 3000lbs.

Cut the range to 33% to turn range in radius to be conservative and the twin engine bombers were carrying a heavier payload a LOT further than the P-38 could.

Special missions like Polesti aside the P-38 didn't offer enough flexibility or range in day to day operations.

 

[BiffF15]

Okay, how did the "bombadier" in the Droop Snoot actually bail out if needed?

Cheers,
Biff

 

[tomo pauk]

Thanks again. Do you know something about historic bomb-runs made by B-25/26, that involved greater range, against, say, a 500-miles distant target and return to same base? Was the 2000 LB bomb ever used on the P-38s, the racks being allowed to carry those?
The P-38L with 300 gal drop tank offers some interesting numbers. After allowance (60 gals for warm-up, taxi, take off to 5000 ft) was accounted for, and with one drop tank (another is replaced with a bomb), it was capable for 1510 miles of range with 650 gals (ie. 300 gals in a DT and 350 gals internal; balance of 60 gals used as allowance). That's how they reached Ploesti (1000 lb bomb on another rack). The 300 gal drop tank (full) weighted 1887 lbs.

Special missions like Polesti aside the P-38 didn't offer enough flexibility or range in day to day operations.

Seems like this one has both flexibility and range?

 

[rinkol]

There is a big difference between the two planes - the Mosquito carried its bomb and fuel load internally whereas the P-38 would have had to carry its bomb load and at least some of its fuel load externally. The performance loss from the external loads would be a serious handicap in any environment where serious airborne opposition could be expected. Also, the second crew member in the Mosquito was useful in that he could carry out a visual search for enemy aircraft as well as performing bomb aiming and navigation.

 

[norab]

Okay, how did the "bombadier" in the Droop Snoot actually bail out if needed?

Cheers,
Biff

 

[model299]

The books and articles I've read about those droop snoots say that position was cramped, and the assignment usually went to men of small stature.

 

[tomo pauk]

There is a big difference between the two planes - the Mosquito carried its bomb and fuel load internally whereas the P-38 would have had to carry its bomb load and at least some of its fuel load externally. <snip> Also, the second crew member in the Mosquito was useful in that he could carry out a visual search for enemy aircraft as well as performing bomb aiming and navigation.

The Mosquito was a bomber from get-go, later modified to other roles and usually excelled there. P-38 was a fighter that was sometimes modified in other roles - there is no doubt that a 'proper' bomber will be better suited for a job than a fighter pressed in that role. Also, the P-38's twin boom configuration precluded easy modifications - the fuselage was not just too narrow (fighter legacy), but also too short. I guess shoehorning a bomb bay would've been quite a task.

The performance loss from the external loads would be a serious handicap in any environment where serious airborne opposition could be expected.

Agreed. The P-38L, with 2x165/150 gal tanks was able to do only 276 mph at 15000 ft on 'maximum weak mixture' (UK term; 'maximum speed on auto-lean' would be the American term), vs. 320 mph for the Mosquito B.IV under same conditions. And that was not the draggiest configuration of the P-38. The speed for maximum range was 229 mph (other conditions are same), vs. Mossie's 265 mph. Having guns vs. not having them ought to cost speed (10-20 mph?), along with space for some fuel.

 

[Shortround6]

The Mosquito was a bomber from get-go, later modified to other roles and usually excelled there. P-38 was a fighter that was sometimes modified in other roles - there is no doubt that a 'proper' bomber will be better suited for a job than a fighter pressed in that role. Also, the P-38's twin boom configuration precluded easy modifications - the fuselage was not just too narrow (fighter legacy), but also too short. I guess shoehorning a bomb bay would've been quite a task.

The same goes for most any plane designed as a "fighter". A bomb bay needs to go about on the center of gravity (especially if the load is more than a few hundred pounds).

from Wiki; "Yak-9B
Fighter-bomber version of Yak-9D (factory designation Yak-9L) with four vertical tube bomb bays aft of the cockpit with capacity for up to 4 × 100 kg (220 lb) FAB-100 bombs or 4 PTAB cassettes with 32 × 1.5 kg (3.3 lb) bomblets each, although normally only 200 kg (440 lb) of weapons were carried in the front bomb bays. Poor handling with a full bomb and fuel load and lack of special aiming equipment limited combat usefulness."

The P-38 only becomes viable with the J model, both because of the engines (more powerful than the earlier planes except the H) and the change in the inter-coolers and fuel tanks (H has 300 US gal internal). The G had 100-200hp less per engine for take-off and while rated for a 1600lb bomb under each wing in later "G" versions that bomb was pretty useless for most purposes.

 

[tomo pauk]

The P-38G have had 1325 HP for take-off, the -H, -J and -L have had 1425, ie. 100 HP difference. Much of the extra T.O. power was needed to cater for greater take off weight - with 2 x 300 gal tanks it was 21400 lbs (P-38J and -L) vs. 19500 lbs (P-38G).
The -G was capable for range of 1870 miles with two 150 gal tanks, the -J and L were good for 1770 with 2 x 165 tanks (fuel allowance from war up to climb to 5000 ft: 48 vs 60 gals). Respective speeds at 20000 ft : 250 mph vs. 244. So the G was at least as 'rangy' as later versions, those being heavier, draggier and using more fuel for take off.
Further, the late war manual for the P-38 lists the 'installations to carry 2 bombs up to 2000 lbs each'. The 1x1000 + 1x500 lbs bombs on one side was also feasible, as it was 4 x 500 lbs bombs and 2 x 150/165 gal tanks.

added: the tables (engine power, take off, range) for the P-38G and earlier can be found in this thread:here
-for the H, J and L - here

edit: the table (linked above) list the take off power for the P-38G as 1240 HP, not 1325. However, the table also allows the use of military power (51in Hg, 3000 rpm), or 1425 HP in case of 'war emergency take off'

 

[Shortround6]

Yep and the table for the G shows 1240hp for take off at 44.5 in at 3000rpm. Using 1425hp was considered a War Emergency Take-off and would require noting in log book and decisions on extra maintenance. (how many WE T-O before quicker plug change,etc).

A P-38G at 19,500lb requires 3130 ft to clear 50ft with zero wind on a 0 degree day.
A P-38H at 19,500lb requires 2220 ft to clear 50ft with zero wind on a 0 degree day.
A P-38J/L at at 19,400lb requires 2190ft to clear 50ft with zero wind on a 0 degree day.

The G, at least at the time the chart was printed was allowed to climb at 2800rpm at 44in.
The H and up were allowed to use 54in at 3000rpm.

If you want it for a bomber you have the same problem as the escort fighter, it doesn't matter what the range is with the big drop tanks. What matters is how far you can fly and how fast with the bombs/drop tanks gone.
The G could do 830 miles on 260 US gallons at 275mph true at 15,000ft with just one set of tank supports.
The J could do 1000 miles on 360 US gallons at 269mph true at 15,000ft with just one set of tank supports or 810 miles at 298mph.

Kicking the speed up cuts things a bit. 335mph for the G cuts the range to 530 miles while while 323mph for the J cuts the range to 600 miles.

Please note that the ranges for the G include a 12 gallon reserve ( a bit small) while the J doesn't include a reserve. Neither range includes any sort of combat allowance and while on a "bomber" mission you don't need ( or hope you don't need) the standard 20 minute allowance a few minutes at full military power would not be beyond of prudent planning. one minute of military power could be worth 3-4 minutes of medium cruise and 5 minutes off most economical.

On the G the carriage of two under wing stores ( drop tanks 150 gal or under or 1100lb (?) bombs) slows the plane by about 10% (305mph down to 275mph) at the same engine settings and fuel burn. 300 gallon drop tanks drop the speed another 15mph at the same settings/fuel burn.
A "G" with two underwing bombs has a "practical" radius of around 250 miles give or take depending on desired cruise speeds, reserve, and combat allowance. It could be around 200 miles depending on altitude ( fuel used in climbing) , cruising speed, reserve desired and time to form up the formation/s.

Carrying a single bomb and a drop tank extends things quite a bit. Trying to carry multiple bombs and drop tanks runs up the drag.

BTW Early B-25s (C-1 and D-1s started) had under wing racks for 6-8 bombs of 100-325lbs. eight 250lbs bombs could be carried outside and 2 1000lb or six 500lb inside for short range work. A 1000lb bomb or two 500lb bombs could be traded for a 215 gal self sealing tank in the top of the bomb bay for longer range work. Much later planes got a rack for a 3rd 1000lb bomb. Max small bombs could be twelve 100lbs inside and eight outside for total of 20.

P-38s could bomb and do special missions but they are not a substitute for a medium bomber.

 

[FLYBOYJ]

There is a big difference between the two planes - the Mosquito carried its bomb and fuel load internally whereas the P-38 would have had to carry its bomb load and at least some of its fuel load externally. The performance loss from the external loads would be a serious handicap in any environment where serious airborne opposition could be expected. Also, the second crew member in the Mosquito was useful in that he could carry out a visual search for enemy aircraft as well as performing bomb aiming and navigation.

If the Mosquito is used in the same medium/ high altitude capacity as a P-38 "Droop Snoot," this is a mute point as during the bomb run the entire formation would have to slow down so the bomb load could be directed and dropped by the lead plane (I think a maximum bomb run speed for the Norton Bomb sight was 180 mph). This is what was done during the P-38 raids on Ploesti. Once bombs were released the lead aircraft with the bombardier left the area while the rest of the flight was free to engage fighters.

 

[tomo pauk]

Yep and the table for the G shows 1240hp for take off at 44.5 in at 3000rpm. Using 1425hp was considered a War Emergency Take-off and would require noting in log book and decisions on extra maintenance. (how many WE T-O before quicker plug change,etc).

Agreed, the 'no free lunch' applies as always. Wonder what a take off with ~1350 HP would've been accounted for?

A P-38G at 19,500lb requires 3130 ft to clear 50ft with zero wind on a 0 degree day.
A P-38H at 19,500lb requires 2220 ft to clear 50ft with zero wind on a 0 degree day.
A P-38J/L at at 19,400lb requires 2190ft to clear 50ft with zero wind on a 0 degree day.

The Boston IV (A-20K?) needed 1500 yds to clear 50 ft obstacle - 4500 ft - on max TO weight (2000 lbs bomb, 605 imp gals of fuel, minus 65 gals as allowance, range 1570 miles). The P-47D needed 5000 ft if the take off weight went to 18000 lbs.
The P-38 with 300 gal drop tank and a 1000 (1100?) lb bomb will shave 1000 lbs from TO weight, meaning the runaway will be 200-500 ft smaller. So a take off run will hardly be a deal breaker, even if the later P-38s can do better.
BTW, what is the P-38 lacking of it's taking off with 19400 lbs? If it has less fuel aboard, it's mileage is still worse than of P-38G, so it will not get as far with same payload.

The G, at least at the time the chart was printed was allowed to climb at 2800rpm at 44in.
The H and up were allowed to use 54in at 3000rpm.

All fair. We are going out to bomb someone, though, not to intercept someone

If you want it for a bomber you have the same problem as the escort fighter, it doesn't matter what the range is with the big drop tanks. What matters is how far you can fly and how fast with the bombs/drop tanks gone.
The G could do 830 miles on 260 US gallons at 275mph true at 15,000ft with just one set of tank supports.
The J could do 1000 miles on 360 US gallons at 269mph true at 15,000ft with just one set of tank supports or 810 miles at 298mph. Kicking the speed up cuts things a bit. 335mph for the G cuts the range to 530 miles while while 323mph for the J cuts the range to 600 miles.

Thanks for the numbers. The 'return range' of 500-700 miles + reserve would've been great for a heavy fighter pressed into bombers role. The later planes are always better than earlier, the earlier planes have better timing, however.

Please note that the ranges for the G include a 12 gallon reserve ( a bit small) while the J doesn't include a reserve. Neither range includes any sort of combat allowance and while on a "bomber" mission you don't need ( or hope you don't need) the standard 20 minute allowance a few minutes at full military power would not be beyond of prudent planning. one minute of military power could be worth 3-4 minutes of medium cruise and 5 minutes off most economical.
On the G the carriage of two under wing stores ( drop tanks 150 gal or under or 1100lb (?) bombs) slows the plane by about 10% (305mph down to 275mph) at the same engine settings and fuel burn. 300 gallon drop tanks drop the speed another 15mph at the same settings/fuel burn.
A "G" with two underwing bombs has a "practical" radius of around 250 miles give or take depending on desired cruise speeds, reserve, and combat allowance. It could be around 200 miles depending on altitude ( fuel used in climbing) , cruising speed, reserve desired and time to form up the formation/s.
Carrying a single bomb and a drop tank extends things quite a bit. Trying to carry multiple bombs and drop tanks runs up the drag.

Agreed.

BTW Early B-25s (C-1 and D-1s started) had under wing racks for 6-8 bombs of 100-325lbs. eight 250lbs bombs could be carried outside and 2 1000lb or six 500lb inside for short range work. A 1000lb bomb or two 500lb bombs could be traded for a 215 gal self sealing tank in the top of the bomb bay for longer range work. Much later planes got a rack for a 3rd 1000lb bomb. Max small bombs could be twelve 100lbs inside and eight outside for total of 20.

P-38s could bomb and do special missions but they are not a substitute for a medium bomber.

Thanks again for the numbers. The B-25s were not available always and everywhere (the Western Allies were using P-40s and P-47s as bombers as often as needed, along with Hurricanes, Spitfires, Blenheims, Marylands, Baltimores etc), while being in dire peril if tried to do some bombing where competent defense was to be encountered. Do you have some data about B-25s doing longer range bombing, against targets 500-600 miles away?